Wednesday, May 11, 2011

Bouncing Jello at 6,200 Frames/Second

Viscoelasticity in action: I'm amazed by how soft the gel is, and yet how it still holds together. It undergoes a very large deformation, very quickly, which suggests that the modulus would increase preventing such strains.

We don't have any bearings as to size of the cubes other than when the finger shows up near the end, and then the cube looks to have dimensions of about 1.5 inches (three fingers). Regardless, for the bouncing cubes, the gel distorts to a minimal thickness of about 5% of the original size. Assuming that volume is conserved, then the spread in the other directions would be about the square root of 20 ~ about a 450% increase in the remaining directions!

I also find the fine details and vibrations on the surface interesting - the surface is not smooth, although I suspect that that is the result of cutting the cube. I don't have a jello salad in front of me now, but I seem to recall that cut jello is not normally smooth. Regardless, there are still deformations occurring at range of scales, all of which would be a lot of fun to measure and quantify if I had the right instrumentation.

3 comments:

Have you tried observing the same thing in a near vacuum? Sydney Nagel at UChicago has done similar experiments on water droplets, they found some interesting results; http://nagelgroup.uchicago.edu/Nagel-Group/Fluids.html